ardupilot/libraries/AP_InertialSensor/AP_InertialSensor_Oilpan.cpp

#include "AP_InertialSensor_Oilpan.h"

// ADC channel mappings on for the APM Oilpan
// Sensors: GYROX, GYROY, GYROZ, ACCELX, ACCELY, ACCELZ
const uint8_t AP_InertialSensor_Oilpan::_sensors[6] = { 1, 2, 0, 4, 5, 6 };

// ADC result sign adjustment for sensors.
const  int8_t AP_InertialSensor_Oilpan::_sensor_signs[6] =
                                            { 1, -1, -1, 1, -1 , -1 };

// ADC channel reading the gyro temperature
const uint8_t AP_InertialSensor_Oilpan::_gyro_temp_ch = 3;

// Maximum possible value returned by an offset-corrected sensor channel
const float AP_InertialSensor_Oilpan::_adc_constraint = 900;

// ADC : Voltage reference 3.3v / 12bits(4096 steps) => 0.8mV/ADC step
// ADXL335 Sensitivity(from datasheet) => 330mV/g,
// 0.8mV/ADC step => 330/0.8 = 412
// Tested value : 418
// 1G in the raw data coming from the accelerometer
// Value based on actual sample data from 20 boards
const float AP_InertialSensor_Oilpan::_gravity = 423.8;

///< would like to use _gravity here, but cannot
const float AP_InertialSensor_Oilpan::_accel_scale = 9.80665 / 423.8;

#define ToRad(x) (x*0.01745329252)  // *pi/180
// IDG500 Sensitivity (from datasheet) => 2.0mV/degree/s,
// 0.8mV/ADC step => 0.8/3.33 = 0.4
// Tested values : 0.4026, ?, 0.4192
const float AP_InertialSensor_Oilpan::_gyro_gain_x = ToRad(0.4);
const float AP_InertialSensor_Oilpan::_gyro_gain_y = ToRad(0.41);
const float AP_InertialSensor_Oilpan::_gyro_gain_z = ToRad(0.41);

/* ------ Public functions -------------------------------------------*/

AP_InertialSensor_Oilpan::AP_InertialSensor_Oilpan( AP_ADC * adc ) :
  _adc(adc)
{
  _gyro.x = 0;
  _gyro.y = 0;
  _gyro.z = 0;
  _accel.x = 0;
  _accel.y = 0;
  _accel.z = 0;
}

void AP_InertialSensor_Oilpan::init( AP_PeriodicProcess * scheduler)
{
  _adc->Init(scheduler);
}

bool AP_InertialSensor_Oilpan::update()
{
  uint16_t adc_values[6];

  _sample_time = _adc->Ch6(_sensors, adc_values);
  _temp = _adc->Ch(_gyro_temp_ch);

  _gyro.x = _gyro_gain_x * _sensor_signs[0] * _gyro_apply_std_offset( adc_values[0] );
  _gyro.y = _gyro_gain_y * _sensor_signs[1] * _gyro_apply_std_offset( adc_values[1] );
  _gyro.z = _gyro_gain_z * _sensor_signs[2] * _gyro_apply_std_offset( adc_values[2] );

  _accel.x = _accel_scale * _sensor_signs[3] * _accel_apply_std_offset( adc_values[3] );
  _accel.y = _accel_scale * _sensor_signs[4] * _accel_apply_std_offset( adc_values[4] );
  _accel.z = _accel_scale * _sensor_signs[5] * _accel_apply_std_offset( adc_values[5] );

  return true;
}

float AP_InertialSensor_Oilpan::gx() { return _gyro.x; }
float AP_InertialSensor_Oilpan::gy() { return _gyro.y; }
float AP_InertialSensor_Oilpan::gz() { return _gyro.z; }

void AP_InertialSensor_Oilpan::get_gyros( float * g )
{
  g[0] = _gyro.x;
  g[1] = _gyro.y;
  g[2] = _gyro.z;
}

float AP_InertialSensor_Oilpan::ax() { return _accel.x; }
float AP_InertialSensor_Oilpan::ay() { return _accel.y; }
float AP_InertialSensor_Oilpan::az() { return _accel.z; }

void AP_InertialSensor_Oilpan::get_accels( float * a )
{
  a[0] = _accel.x;
  a[1] = _accel.y;
  a[2] = _accel.z;
}

void AP_InertialSensor_Oilpan::get_sensors( float * sensors )
{
  sensors[0] = _gyro.x;
  sensors[1] = _gyro.y;
  sensors[2] = _gyro.z;
  sensors[3] = _accel.x;
  sensors[4] = _accel.y;
  sensors[5] = _accel.z;
}

float AP_InertialSensor_Oilpan::temperature() { return _temp; }

uint32_t AP_InertialSensor_Oilpan::sample_time() { return _sample_time; }
void AP_InertialSensor_Oilpan::reset_sample_time() { }

/* ------ Private functions -------------------------------------------*/

float AP_InertialSensor_Oilpan::_gyro_apply_std_offset( uint16_t adc_value )
{
  /* Magic number from AP_ADC_Oilpan.h */
  return ((float) adc_value ) - 1658.0f;
}

float AP_InertialSensor_Oilpan::_accel_apply_std_offset( uint16_t adc_value )
{
  /* Magic number from AP_ADC_Oilpan.h */
  return ((float) adc_value ) - 2041.0f;
}